Non-rechargeable batteries are known as primary batteries while rechargeable batteries are known as secondary batteries. A secondary battery is capable of repeatedly being charged, storing the charge and delivering the charge to a medical device, such as a surgical tool, to which the battery is attached. Secondary batteries have, over the years, evolved into reliable power sources for powered surgical tools used in operating rooms to perform surgical procedures. The use of a battery eliminates the need to provide a power cord connected to an external power source. The elimination of the power cord offers benefits over corded surgical tools. Surgical personnel using this type of tool do not have to concern themselves with either sterilizing a cord so that it can be brought into the sterile surgical field surrounding the patient or ensuring that, during surgery, an unsterilized cord is not inadvertently introduced into the surgical field. Moreover, the elimination of the cord results in the removal of the physical clutter and field-of-view blockage the cord otherwise brings to a surgical procedure.
A secondary battery typically includes a housing and one or more rechargeable cells disposed in the housing. The cells are formed from material capable of storing electrical charge.
Batteries used to power surgical tools are exposed to adverse environmental elements to which batteries used for non-medical uses are seldom exposed. For example, during a surgical procedure, a medical battery may be exposed to blood or other body fluid. Tissue removed from the patient may adhere to the battery. While not an intended part of any procedure, the battery may be exposed to a saline solution. To eliminate the risk of patients being infected during the course of the medical procedure, it is therefore standard practice to sterilize the battery between surgical procedures. This cleaning/sterilization process typically involves rinsing the battery to remove contaminates that are readily visible on the surface of the battery. However, these events may cause a conductive bridge to form between the battery contacts, which can lead to the formation of a layer of metal oxide on one or more of the contacts. This oxide layer functions as an impedance layer that reduces the efficiency of both the charging of the battery and the efficiency of the battery to deliver charge to the tool to which the battery is coupled.
The batteries may also be subjected to immersion in a steam-filled chamber as part of an autoclaving process. To survive the high temperatures present during the autoclaving process, specialized batteries must be used. Autoclave temperatures often exceed 130 degrees centigrade. Even with specialized batteries that are designed to withstand autoclave temperatures, damage may still occur to the batteries during the autoclave process (although less damage than would occur with conventional batteries used in other environments). As a result, batteries used in medical environments that are subjected to autoclaving may sustain more damage than batteries used in other industries.